package com.hmdp.utils;

import cn.hutool.core.lang.func.Func;
import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.annotation.Id;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {

    @Resource
    private  StringRedisTemplate stringRedisTemplate;

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    //带逻辑过期的写入
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //缓存穿透
    //Function<ID,R>,方法的参数类型，和返回值类型
    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit){
        String key = keyPrefix + id;
        //1、从redis查询点评缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2、判断是否存在
        if (!StrUtil.isBlank(json)) {
            //3、存在,直接放回数据
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if(json != null){
            return null;
        }
        //4、不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5、不存在,返回错误
        if (r == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6、存在，写入redis
        this.set(key, r, time, unit);
        //7、返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    //缓存击穿
    public <R,ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> adFallback, Long time, TimeUnit unit){
        String key = keyPrefix + id;
        //1、从redis查询点评缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2、判断是否存在
        if (StrUtil.isBlank(json)) {
            //3、未命中,直接放回数据
            return null;
        }

        //4、命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5、判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1 未过期，直接返回店铺信息
            return r;
        }
        //5.2 已过期，需要缓存重建
        //6、缓存重建
        //6.1 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2 判断是否获取锁成功
        if (isLock){
            //6.3 成功，开启独立线程，实现缓存重现
            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {
                    //查询数据库
                    R r1 = adFallback.apply(id);
                    //System.out.println(r1);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        // 6.4 放回过期的店铺信息
        return r;
    }

    //获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

}
